Russia's Foreign Ministry has rejected a draft UN Security Council resolution condemning an apparent chemical-weapons attack in Syria’s Idlib Province that left dozens killed and injured.

Foreign Ministry spokeswoman Maria Zakharova said on April 5 that the resolution -- drafted by the United States, Britain, and France -- was "categorically unacceptable" and obviously was drawn up in haste.

The UN Security Council is holding emergency session to discuss the attack.

"The UN Security Council's draft resolution is anti-Syrian and can lead to more escalation in Syria and in the region as a whole," Zakharova also said.

At the same time, the international community continued to express condemnation of the government of Syrian President Bashar al-Assad. British Foreign Secretary Boris Johnson noted the hundreds of thousands of people who have died during Syria’s six-year civil war and said Assad "is responsible for the vast majority of the butcher’s bill."

European Council President Donald Tusk said "the Syrian regime bears the primary responsibility for the atrocities." He added that "those who support the regime" share that responsibility.

Russia, a key backer of the Syrian government in its war against opponents, said on April 5 that Syrian planes had attacked the town of Khan Sheikhoun in Idlib Province and asserted that the aircraft struck a weapons depot and ammunition factory. The Syrian government issued a similar statement the previous day.

WATCH: The British ambassador to the United Nations, Matthew Rycroft, strongly criticized Russia during a UN Security Council debate, suggesting previous Russian vetoes of resolutions against Syria had emboldened the Assad regime:

In a statement on YouTube, Russian Defense Ministry spokesman Major General Igor Konashenkov claimed that the factory produced chemical weapons that were used in Iraq.

Konashenkov also claimed that the chemical munitions were used by rebels in the Syrian city of Aleppo last year.

A rebel commander called the Russian statement a lie, and a spokeswoman for German Chancellor Angela Merkel said that Russia and Iran bear a share of responsibility for the attack because they back Assad.

Later, air strikes allegedly targeted medical facilities where victims of the attack were being treated.

A child receives treatment at a field hospital after an alleged chemical-weapons attack in Idlib on April 4.

The Syrian Observatory for Human Rights increased the death toll from the alleged chemical attack to 72. Half of those killed were children or women.

The Britain-based monitoring group was unable to say what chemical was involved, but local medical personnel said they suspected it was the nerve agent sarin.

Some victims appeared to show symptoms consistent with reaction to a nerve agent, the World Health Organization said on April 5.

Footage from the scene showed civilians choking and foaming at the mouth.

The symptoms of the victims shown on videos in social networks are "the same as they were in autumn of the previous year in Aleppo," Konashenkov said.

The Syrian government statement on April 4 said the attack was carried out by Russian-made Sukhoi Su-22 fighter bombers, which it said are not capable of deploying chemical weapons.

Russia has given Assad crucial military and diplomatic backing throughout the 6-year-old war in Syria, and stepped up its support by launching a campaign of air strikes against government opponents in September 2015.

Moscow and Damascus’s claims have also received support from officials and state media in Iran, another key backer of Assad.

However, a commander of the Free Idlib Army rebel group, Hasan Haj Ali, called the Russian statement a "lie."

"Everyone saw the plane while it was bombing with gas," he told the Reuters news agency.

"There are no military positions there, or places for the manufacture [of weapons]," Ali added. "The various factions of the opposition are not capable of producing these substances."

A UN-led investigation has concluded that the Syrian government used chlorine as a weapon at least three time in 2014 and 2015. Damascus denied the charge, blaming rebel fighters.

Russia has blocked several previous resolutions that could have undermined Assad.

Russian President Vladimir Putin's spokesman, Dmitry Peskov, said on April 5 that "as part of its argument," Russia would "present the facts which have already been laid out by our Defense Ministry."

He said the Russian military would continue what he called its "counterterrorist" operations in Syria.

French President Francois Hollande called on April 5 for "a reaction by the international community commensurate with this war crime," his office said in a statement.

Germany said it expected that "Russia, in the UN Security Council and elsewhere, not interfere in the search for those responsible ... but actively support it."

Iranian Foreign Ministry spokesman Bahram Ghasemi said on April 5 that Tehran "condemns any use of chemical weapons, regardless of who has used it and who are the victims."

He also called for "the chemical disarmament of armed terrorist groups."

On April 4, U.S. President Donald Trump denounced the attack as a "heinous" act by the Assad regime that "cannot be ignored by the civilized world."

He pointed the finger at his predecessor, Barack Obama, accusing Obama of "weakness and irresolution" on Syria.

UN Syrian envoy Staffan de Mistura said all indications were that "it was a chemical attack and it came from the air."

In Brussels, representatives from some 70 donor countries and organizations gathered on April 5 to drum up billions of dollars in aid for war-ravaged Syria.

Opening the conference, UN Secretary-General Antonio Guterres appealed for Syria's warring factions and their international backers to set aside their differences and bring an end to the conflict.

"Nobody is winning this war; everybody is losing," Guterres said. "It is having a detrimental and destabilizing effect on the entire region and it is providing a focus that is feeding the new threat of global terrorism."

At least 300,000 people have been killed and millions displaced by the war in Syria, which began with a government clampdown on pro-democracy protests in 2011.